Size-exclusion chromatographic descriptors of humic substances

An approach to the generation of size exclusion chromatographic (SEC) descr iptors of humic substances (HS) is proposed. It implies a calculation of in itial, central and normalised statistical moments and some of their ratios from the raw SEC-data. The proposed descriptors extend the pool of common m olecular weight (MW) characteristics (average MW's and their ratios) up to 20 parameters, which is important for the purposes of classification and pr ognostic modelling. Original software was developed to facilitate the compu tation of molecular weight distribution (MWD) and SEC-descriptors of HS fro m raw chromatographic data. The developed approach was applied to two model compounds and three humic materials. The discriminatory power of the calcu lated descriptors was roughly estimated on the example of three humic mater ials of different origin with the use of a multivariate variance analysis. Weight average MW and a ratio of the z- to weight average distribution coef ficients were found to be the best discriminators, whereas the significance level of discrimination provided by the second moment and M-z/M-w-ratio wa s lower than 95%. (C) 2000 Elsevier Science B.V. All rights reserved.